The present invention generally relates to an implantable cardiac stimulation system and more particularly to a three lead universal defibrillation and pacing system capable of providing defibrillating and pacing pulses to all four chambers of the heart. The present invention is further directed to such a system having two leads implantable in the coronary sinus region of the heart to permit implementation of the universal defibrillation and pacing system.
Implantable cardiac stimulation devices are well known in the art. Such devices may include, for example, implantable cardiac pacemakers and defibrillators. The devices are generally implanted in a pectoral region of the chest beneath the skin of a patient within what is known as a subcutaneous pocket. The implantable devices generally function in association with one or more electrode carrying leads which are implanted within the heart. The electrodes are usually positioned within the right side of the heart, either within the right ventricle or right atrium, or both, for making electrical contact with their respective heart chamber. Conductors within the leads and a proximal connector carried by the leads couple the electrodes to the device to enable the device to sense cardiac electrical activity and deliver the desired therapy.
Traditionally, therapy delivery had been limited to the venous, or right side of the heart. The reason for this is that implanted electrodes can cause blood clot formation in some patients. If a blood clot were released arterially from the left heart, as for example the left ventricle, it could pass directly to the brain potentially resulting in a paralyzing or fatal stroke. However, a blood clot released from the right heart, as from the right ventricle, would pass into the lungs where the filtering action of the lungs would prevent a fatal or debilitating embolism in the brain.
Recently, new lead structures and methods have been proposed and even practiced for delivering cardiac rhythm management therapy to the left heart. These lead structures and methods avoid direct electrode placement within the left atrium and left ventricle of the heart by lead implantation within the coronary sinus region of the heart. As used herein, the phrase xe2x80x9ccoronary sinus regionxe2x80x9d refers to the venous vasculature of the left ventricle, including any portions of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus.
It has been demonstrated that electrodes placed in the coronary sinus region of the heart may be used for left atrial pacing, left ventricular pacing, or cardioversion and defibrillation. These advancements enable implantable cardiac stimulation devices to address the needs of a patient population with left ventricular dysfunction and/or congestive heart failure which would benefit from left heart side pacing, either alone or in conjunction with right heart side pacing (bi-chamber pacing), and/or defibrillation.
Universal pacing and/or defibrillation systems capable of pacing and/or defibrillating all of the chambers of the right and left heart would of course require numerous pacing and/or defibrillation electrodes to be employed within the heart and its coronary venous system. Providing the numerous electrodes to implement such universal heart stimulation systems would in turn require an inordinate number of leads if currently available right and left heart leads were employed. This would result in unduly long implant procedures and possibly more leads than the human anatomy is able to accommodate. The number of leads required may also make it difficult to accurately locate each electrode at its most efficacious position within the heart.
Hence, there is a need in the art for new and improved right and left heart leads and lead configurations which provide efficient left heart access and integrated right and left heart therapies. Electrode placement on the leads should enable effective therapy and electrode selection to accommodate differences in heart physiology from one patient to another. Universal pacing and defibrillation systems that would result from the new and improved leads and lead configurations could provide significant improved therapies. Coordinated right heart and left heart pacing therapies would be made possible. Further, improved defibrillation therapies would also be made possible. The therapies could provide improved electrode configuration selection for improved defibrillation energy distribution within the heart or support improved sequential defibrillation pulse techniques. The present invention is directed to left heart leads and right and left heart lead configurations which address the above mentioned needs.
The invention provides an implantable cardiac stimulation system for delivering stimulation pulses to any one chamber or combination of chambers of a heart. The system includes a lead system consisting of a first lead for implant in the right ventricle and having a right ventricular defibrillation electrode, a second lead for implant in the coronary sinus and having a left ventricular defibrillation electrode for placement in electrical contact with the left ventricle adjacent to the left ventricle and within the coronary sinus, and a third lead for implant in the coronary sinus and having a left atrial defibrillation electrode for placement in electrical contact with the left atrium adjacent to the left atrium and within the coronary sinus. One of the leads further includes a right atrial defibrillation electrode for placement in one of the right atrium and superior vena cava. The system further includes an implantable cardiac stimulation device including a programmable pulse generator that delivers defibrillation pulses to any one of the defibrillation electrodes or to any combination of the defibrillation electrodes.
In accordance with further aspects of the invention, the first lead may include a right ventricular pacing electrode or bipolar electrode pair and the pulse generator is programmable to deliver pacing pulses to the right ventricular pacing electrode or bipolar electrode pair. The second lead further include a left ventricular pacing electrode or bipolar electrode pair for placement in electrical contact with the left ventricle and the pulse generator is programmable to deliver pacing pulses to the left ventricular pacing electrode or bipolar electrode pair. The third lead may further include at least one left atrial pacing electrode for placement in electrical contact with the left atrium and the pulse generator is programmable to deliver pacing pulses to the at least one left atrial pacing electrode. The third lead may still further include at least one right atrial pacing electrode for placement in electrical contact with the right atrium and the pulse generator is programmable to deliver pacing pulses to either one or both of the atrial pacing electrodes. The atrial pacing electrodes are preferably spaced apart on the lead so that when the left atrial pacing electrode is in electrical contact with and adjacent the left atrium within the coronary sinus, the at least one right atrial pacing electrode is in electrical contact with the right atrium and adjacent to the ostium of the coronary sinus within the coronary sinus.
In accordance with still further aspects of the invention, the defibrillation electrodes are preferably coil electrodes. The device may further include a conductive case and the pulse generator may be programmable to deliver stimulation pulses between any one of the defibrillation electrodes and the case.